Mr Blandings Builds His Dream House is an amiable 1948 comedy that casts Cary Grant as an imperilled advertising executive who is rescued, on the day of the deadline, by his beaming black domestic servant. "If you ain't eating Wham, you ain't eating ham," quips the servant, bustling in with a freshly prepared breakfast and casually providing a slogan to save her master's bacon. Naturally Blandings is delighted. "Darling!" he calls to his wife. "Give Gussie a $10 raise." This, back in 1948, was what passed for a Hollywood happy ending.

These days, thank heaven, the help are paid more fairly. For evidence, check out The Help, a 60s-set, Mississippi-based drama about a bunch of servants who "help" a white journalist write a book and then go on to share in the royalties. Over in the US, Tate Taylor's film – an adaptation of his friend Kathryn Stockett's novel – has bloomed into a word-of-mouth hit, a watercooler discussion point, and sat atop the box office chart for 25 days straight.

Everyone, it seems, has an opinion on The Help. For the fans, it's big-hearted and gently radical, a film that gives a voice to the dispossessed while posing as a white girl's coming-of-age tale. For its detractors, however, it's a reductive essay in racial profiteering, another slice of the same old ham. According to a statement released by the Association of Black Women Historians: "The Help distorts, ignores and trivialises the experiences of black domestic workers." Far from being empowered and liberated, The Help's domestic drudges represent "a disappointing resurrection of Mammy".

Call her Gussie or Beulah, Jemima or Dinah. Call her to fix your supper or raise your kids. Her true name is the M-word and that's old as Hollywood itself. She was there at the start, defending her owners from Union soldiers in DW Griffith's Birth of a Nation, or being serenaded by a blackfaced Al Jolson in The Jazz Singer, or scolding Scarlett O'Hara through the ups and downs of Gone With the Wind. And along the way, her basic contours remained the same. Mammy was stoic and loyal. She lived to help and and her greatest reward was a smile (pre-reconstruction) or a few extra dollars (post-). Anything more was liable to scare her half to death.

Prior to her walk-on part as Gussie, for instance, the African-American actor Louise Beavers cropped up in 1934's Imitation of Life. She played Aunt Delilah, a cook who "makes a present" of her priceless pancake recipe and rejects the offer of a stake in the company. Her mistress tries to explain that she can buy her own car, her own house. But Delilah isn't biting. "My own house?" she splutters. "You gonna send me away, Miss Bea? Oh honey-chile, please don't send me away! I'se your cook and I wants to stay your cook."

Mammy is a fiction and a fantasy; a construct of southern novelists and Hollywood screenwriters, expressly designed to sooth wealthy white viewers with black staff at home. But Mammy does not quite spring out of nowhere. She has her roots in reality, whether that be in the recent past of the Jim Crow-era or the day-to-day routines in affluent homes across 21st-century America. This is what makes The Help so compromised and so fraught with danger. As children, growing up in 1970s Mississippi, director Taylor and writer Stockett were both raised by black nannies. The Help was conceived, in part, as an investigation; an inquiry into the lives and back-stories of the women they knew in their youth. Taylor's former nanny – Carol Lee – even has a small role in the drama.

"All of the criticism we've been facing is based on the fact that I'm not an African-American director and that Kathryn is not an African-American writer," Taylor says. "It suggests that race relations in my country are still very black and white. But outside of a small academic elite, it doesn't matter. The Help has been playing to all four quadrants. All races, ages, sexes have gone to see it. The most profitable theatre of its run has been in Jackson, Mississippi, with a completely mixed audience. And afterwards people stop in the parking lot and talk about the issues."

The Help concerns Skeeter, an aspiring young journalist (Emma Stone), who persuades the servants to open up and air their grievances. "Margaret Mitchell glorified the Mammy figure," Skeeter reasons. "But no one ever asked the Mammy how she thought about it." Her reporting assignment leads us around the porticoed porches and rhododendron bushes and pokes fun at the fragrant, Stepford-style racists who quail at the thought of sharing their bathroom with the "coloured" help. It's 1960s Jackson, so naturally the film has segregated buses and brutish cops, while the plot turns on the assassination of Medgar Evers.

Does that make it a civil rights movie? "No," insists Taylor. "Civil rights is just the backdrop. I'm not qualified to make a film about civil rights. People say to me: 'Why wasn't there a lynching? Why aren't there houses burning down?' But that's not what this story is. For me, the most horrific moment in the film is the scene where the maid is sitting with her panties round her ankles in a three-by-three plywood bathroom, like a cat in a litter-box, while an impatient white woman is tapping her foot outside. If people need to see blood and gore and can't see how horrific that is – well, I don't have answer to that."

But what of the help themselves? On being offered the role of the film's principal maid (steadfast, long-suffering Aibileen), the Oscar-nominated actor Viola Davis admits she had qualms. "Absolutely it was a concern for me," she says. "These kind of roles carry so much stigma within the African-American community. But that's down to the sheer lack of stories that Hollywood tells. Again and again, we revisit the same black characters. The maid, the thug, the drug addict. But the Mammy stereotype only exists in the playing of it and the writing of it. She's never humanised. So she remains a caricature."

In Hollywood's early days, the issue came down to a straight tussle between visibility and representation. Do we celebrate Gone With the Wind star Hattie McDaniel as a trailblazer, the first African-American to win an acting Oscar? Or do we damn her for pandering to racist stereotypes? No doubt McDaniel viewed Mammy as her best – and perhaps only – option in an industry where rewarding roles for black performers were almost non-existent. "Why should I complain about making $7,000 playing a maid?" she once said. "If I didn't, I'd be making $7 a week actually being one."

But can Mammy now be consigned to the dustbin of history? Recent evidence suggests otherwise. Today one may catch glimpses of an old, familiar figure in the knockabout antics of recent hits like Big Momma's House or what Spike Lee derides as the "coonery buffoonery" of cross-dressing Tyler Perry. And, yes, in a fashion she is all over The Help as well: cooking, cleaning and delivering the film's big payload of revenge when she bakes a customised chocolate cake for her reviled white employer. Mammy, against all the odds, endures.

On preparing to play Aibileen, Davis found that her research had largely been done in advance. She was raised, she says, in "abject poverty" – first in South Carolina and then Rhode Island. "My mother, my grandmother and my aunt all worked as maids. Sun-up to sundown, $25 a week. My grandmother delivered me at home because we couldn't afford to go to the hospital. My mother would work her fingers to the bone in the kitchen and then go to work her fingers to the bone in someone else's kitchen. So I know those women. I've heard their stories all my life."

The maid, she says, is not a myth. "And yes, Mammy does exist – if that's what you want to call her. But Mammy is not all she is. So ask the questions. Find out what she thinks, what she's like and who she is beyond the kitchen. That's the challenge for film-makers today."